Polyolefin-based sheet, display sheet comprising the same, package sheet, transparent recording sheet, cosmetic sheet, emblem sheet, decorative sheet, and coating material for polyolefin resin for use in these

ABSTRACT

A polyolefin-based sheet having a coating layer, which improves printability and does not impair adhesion, wherein the coating layer is one formed from a coating material comprising a water-soluble acrylic resin and polyalkylenimine.

TECHNICAL FIELD

[0001] The present invention relates to a polyolefin-based sheet,display sheet comprising the same, package sheet, transparent recordingsheet, cosmetic sheet, emblem sheet, decorative sheet, and coatingmaterial for polyolefin resin for use in these.

BACKGROUND ART

[0002] Recently, in the production of plastic sheets including packagematerials, polyolefin-based substrate sheets (PO sheets) areincreasingly used because of their being compatible with environment.However, in order for a given material to serve as a useful packagematerial, it is often required that it is also amenable to secondaryprocessing: particularly it must be easily printable and adhesive.

[0003] To meet the above requirement, that is, to improve the ease withwhich the PO sheet is amenable to secondary processing, a process isintroduced to modify the surface condition of the PO sheet: the sheet issubjected to an oxidization treatment based on corona discharge, or acoating material comprising polyethylenimine and a resin emulsion isapplied to the sheet.

[0004] However, the treatment based on corona discharge poses a problem:its effect fades over time.

[0005] Applying a coating material to a PO sheet is introduced with anintention to improve the printability of the sheet. However, because thePO sheet is inherently low in printability, the above treatment cannotbring about a notable effect as expected. In addition, the cationicactivity inherent to polyethylenimine may impair the adhesive activityof a cyanoacrylate adhesive agent usually used in the secondaryprocessing.

[0006] Under these situations, there is a need for a PO sheet, which iseasily amenable to printing and bonding.

[0007] In the production of package materials, preparation of sheetsconsists of forming a hologram layer on a substrate sheet such as a POsheet via metal vapor deposition, to enhance the ornamental effect ofthe sheet.

[0008] More specifically, forming a hologram layer on a substrate sheetconsists of (1) preparing a metal film on a transfer material composedof PET or the like; (2) applying, under pressure, the transfer materialto a substrate sheet via an adhesive layer by pressing a roller carryingthe transfer material whose surface has a relief pattern against thesubstrate sheet; and (3) obtaining the substrate sheet having the metalfilm transferred and bonded thereupon with the film having the reliefpattern printed.

[0009] The hologram layer will have its ornamental effect more enhanced,if both of the substrate sheet and the adhesive layer are madelight-transmissive (transparent). The preferred adhesive agent forbonding a metal film to a PO sheet may include urethane-based agents oracrylic agents.

[0010] However, if a urethane-based adhesive agent is used in thisprocess, although the adhesion is secured, the resulting product willhave a limited ornamental effect, because the adhesive is not colorlessnor transparent, On the other hand, if an acrylic adhesive agent is usedin this process, the product will pose a different problem: theornamental layer will be easily torn off because of its inadequateadhesion to the PO sheet, although the product will have a sufficienttransparency. This is problematic in practice.

[0011] One object of the present invention is to provide a coatingmaterial useful for polyolefin-based sheets, which will improve theprintability of the sheet, and not interfere with its adhesive activity,and also to provide display sheets, package sheets, transparentrecording sheets, costume sheets, and emblem sheets based on the use ofsuch coated polyolefin-based sheets.

[0012] Another object of the present invention is to provide apolyolefin-based sheet, which is suitably processed into a sheet havinga metal-containing ornamental layer thereupon in which adhesion of theornamental layer to the sheet is secured while the sheet assembly beingkept transparent, and also to provide ornamental sheets based on the useof such polyolefin-based sheets.

DISCLOSURE OF THE INVENTION

[0013] A polyolefin-based sheet according to this invention ischaracterized by that the sheet has a coating layer made of a coatingmaterial comprising a water-soluble acrylic resin and polyalkylenimine.

[0014] The usable polyolefin resin constituting the PO sheet includeshomopolymers and copolymers of various olefins, and their mixtures. Theusable monomer for homopolymers includes ethylene, propylene, 1-buthane,isoprene, butadiene, etc. The usable copolymer includesethylene-α-olefin copolymers, ethylene-cyclic olefin copolymers,propylene-α-olefin copolymers, ethylene-vinyl acetate copolymers,ethylene-acrylic acid ester copolymers, etc. Of the PO sheets composedof such various PO resins, the preferred one includespolypropylene-based sheets because of their transparency, mechanicalstrength, etc.

[0015] The method by which to prepare a sheet from such a resin mayinclude any known method such as T-die extrusion, calendering, casting,or the like. The PO sheet may consist of a single layer or of multiplelayers. The method for producing multi-layered sheets may includevarious lamination methods such as co-extrusion, thermal lamination,etc.

[0016] The sheet may have both surfaces coated or either of them coated.

[0017] The water-soluble acrylic resin according to this invention mayinclude polymers comprising various unsaturated carboxylic acids, andtheir derivatives. The usable unsaturated carboxylic acid and itsderivatives may include acrylic acid, alkyl acrylate, methacrylic acid,alkyl methacrylate, itaconic acid, maleic acid, fumaric acid, etc.

[0018] The usable polyalkylenimine may include polyethylenimine,polypropylenimine, etc. Of them, polyethylenimine is particularlypreferred. The usable polyethylenimine polymer may include homopolymersof ethylenimine, its modified polymers, and its graft copolymers.

[0019] The PO sheet according to this invention may include a coatingfilm having a relatively small thickness.

[0020] According to the present invention, because the coating materialincludes a water-soluble acrylic resin containing a polymer of anunsaturated carboxylic acid in addition to polyalkylenimine, the coatedPO sheet will be improved in its printability and maintain its secureadhesiveness.

[0021] Because the sheet is improved in printability on account of thecoat containing polyalkylenimine, it is possible to print the sheetassembly using common ink.

[0022] If the coating material comprised only polyalkylenimine, thecoating fluid would be so viscous that, even when it is applied, itwould not give a uniform film but cause blocking. When a water-solubleacrylic resin is added to the above coating material, polyalkylenimineis cross-bridged via ionic bond with the carboxyl group of the acrylicresin, and thus a strong coating film is formed from the resultingcoating material. Moreover, if the coating material comprisespolyalkylenimine and a water-soluble acrylic resin, it is possible tocontrol the content of polyalkylenimine in a coating film by adjustingthe coating amount as appropriate, so that the impaired adhesiveness ofa cyanoacrylate adhesive agent, which would be otherwise encountered asa result of coexistent polyalkylenimine, can be effectively avoided.

[0023] Besides, if another sheet is laid over the coating layer of a POsheet, the resulting laminated structure will be improved in itsmechanical strength.

[0024] The coating layer preferably has a thickness of 0.003 to 0.1 μm,and the preferred blending ratio of the water soluble alkyl resin andpolyalkylenimine is in the range of 5:1 to 1:4.

[0025] If the coating layer had a thickness of less than 0.003 μm, theadvantage obtainable from the coating would be negligible. On the otherhand, if the coating layer had a thickness of more than 0.1 μm,polyalkylenimine would be present in such an excess amount that it wouldinterfere with the adhesive activity of cyanoacrylate.

[0026] If the blending ratio of polyalkylenimine against the watersoluble alkyl resin were less than 5:1, the resulting coat would nothave sufficient adhesion to the PO sheet. On the other hand, if theblending ratio in question were more than 1:4, the resulting coatingwould easily cause blocking when the PO sheets are overlaid to eachother.

[0027] The coating amount (density) of polyalkylenimine is preferably inthe range of 0.0005 to 0.1 g/m², or more preferably 0.0007 to 0.07 g/m².

[0028] The coating amount here is based on the dry weight of coatedpolyalkylenimine, that is, the content of solid polyalkylenimine in anemulsion when, for example, a coating material containingpolyalkylenimine exists as an emulsion.

[0029] If the coating amount were less than 0.0005 g/m², the PO sheetwith such a coat would have degraded printability, and lowered adhesionwhen put into contact with an acrylic adhesive agent. On the other hand,if the coating amount were more than 0.1 g/m², the resulting coat wouldhave lowered adhesion to a cyanoacrylate adhesive agent, and the POsheets with such a coat would easily develop blocking when overlaid toeach other.

[0030] The coating layer preferably contains an antistatic agent: thecontent of the antistatic agent is preferably in the range of 0.5 to 30wt %, or more preferably 2 to 15 wt % with respect to the overall weightof solid components of the coating material.

[0031] The usable antistatic agent may include any arbitrarily chosenantistatic agent such as surfactants (anionic, cationic, non-ionic andampholytic), inorganic salts, polyatomic alcohols, metal compounds, andcarbon, but the preferred one includes anionic surfactants such assodium sulfonate.

[0032] When an antistatic agent is added to the coating material, theresulting coat will be able to prevent static electricity fromaccumulating on its surface, and thus blocking due to the development ofstatic electricity will be safely prevented. Moreover, addition of anantistatic agent to the coating material will effectively lessen theamount of an antistatic agent to be added to the PO sheet material whichwould be otherwise required, thereby avoiding the bleed-out of thatagent which would otherwise result if the sheet containing an otherwiserequired amount of antistatic agent were exposed to high temperatures,that is, the bleed-out which would degrade the appearance of the sheetand its amenability to processing will be effectively avoided.

[0033] The coating material preferably contains a natural organicmaterial fine powder and/or a ultraviolet (UV) ray absorbing agent.

[0034] The usable powdery natural organic material may include collagenin fine powder; silk fibroin in fine powder; cellulose in fine powder;sericine, chitin or chitosan in fine powder; wool in fine powder; linen,cotton or sponge in powder; egg-white; whey; casein; serum protein;gelatin; etc. The solubilized substance from them may be also used.

[0035] The usable UV absorbing agent may include an emulsion obtained bysuspending a copolymer of a benzotriazole-based UV absorbing agent andacryl in a medium.

[0036] When such a natural organic material fine powder is added to thecoating material, the resulting coat will be improved in its surfacesmoothness. When such a UV absorbing agent is added to the coatingmaterial, the resulting coat will prevent the transmission of UV raysthrough it, and thus the degradation of the underlying PO sheet whichwould otherwise brought about by transmitted UV rays, and thedegradation of an article wrapped with the PO sheet if the PO sheetserves as a package material would be safely avoided.

[0037] The polyolefin-based sheet described above is highly transparent,easily amenable to printing, and easily amenable to secondary processingincluding bonding. Moreover, because it is easily provided withfunctions such as anti-static activity, UV ray absorbing activity, etc.,it is suitably used as display sheets, various package sheets,transparent recording sheets, cosmetic sheets, emblem sheets, etc.

[0038] Further, the polyolefin-based sheet described above may be usedas ornamental sheets.

[0039] The aforementioned polyolefin-based sheet preferably comprises apolyolefin-based substrate sheet having a metal-containing ornamentallayer formed at least on one of its surfaces wherein a coating layer isformed on the surface upon which the ornamental layer will be formed,and wherein the coating layer is preferably made from a coating materialcomprising a water-soluble acrylic resin comprising a polymer of anunsaturated carboxylic acid, and polyalkylenimine.

[0040] The polyolefin-based resin constituting the substrate sheet is asdescribed above, but preferably includes polypropylene-based sheetswhose transparency has been enhanced. Specifically, most preferred arethe polypropylene-based sheets whose total haze (overall opacity) is 10%or less when measured by a method based on JIS K7105.

[0041] The unsaturated carboxylic acid preferably includes acrylic acidand/or methacrylic acid.

[0042] The ornamental layer prepared according to the present inventionis not limited to any specific one, but may include various ornamentallayers based on metal films. However, it is preferably a hologram layerobtained by modifying the surface of a metal film to have a reliefpattern.

[0043] The method by which to form an ornamental layer may includevarious ones, for example, a method which consists of forming a metalfilm on a transfer sheet via sputtering, ion-plating, vapor depositionor the like, and of transferring the metal film onto a substrate sheet.Particularly, the method suitable for forming a hologram layer mayinclude a method which consists of forming a metal film on a transfermaterial via vapor deposition, and of transferring the metal film to asubstrate sheet, or a method which consists of directly forming anornamental layer on the surface of a coating layer excellent in adhesionvia gravure coating.

[0044] Transference of a metal film to a substrate sheet may occur byany method chosen as appropriate depending on the property of anadhesive agent to be used in conjunction.

[0045] The metal to be used for the ornamental layer preferably includesnon-iron metals such as aluminum, magnesium, nickel, and chromium, andtheir oxides, and their mixtures.

[0046] According to the present invention, a coating layer composed of acoating material comprising a water-soluble acrylic resin prepared froma polymer of an unsaturated carboxylic acid, and polyalkylenimine coversthe surface of a PO substrate sheet upon which an ornamental layer willbe formed. Accordingly, if an ornamental layer is formed on the coatingsurface of the substrate sheet via an acrylic adhesive agent, adhesionof the ornamental layer to the substrate sheet will be enhanced. Throughthis arrangement it is possible for the ornamental layer to be securelybonded to the PO sheet even when the acrylic adhesive agent is used foradhesion, which would otherwise have a low adhesive activity towards thePO sheet. In addition, because an acrylic adhesive agent is used foradhesion, the sheet assembly will have a high transparency, and themetallic shade of the ornamental layer will serve as an attractivedesign feature when the sheet is used as a package material, that is,the sheet will serve as a highly ornamental package material.

[0047] The ornamental sheet assembly according to this inventioncomprises a polyolefin-based substrate sheet having a coating layercomposed of a coating material comprising a water-soluble acrylic resinand polyalkylenimine, an acrylic adhesive layer formed on the coatinglayer, and an ornamental layer formed on the acrylic adhesive layer.

[0048] According to the present invention, because the PO substratesheet has the coating layer containing polyalkylenimine, adhesion of theacrylic adhesive agent to the PO sheet is enhanced, and, as aconsequence, adhesion of the ornamental layer to the PO sheet is alsoenhanced. In addition, because the acrylic adhesive agent is used, thetransparency of the ornamental sheet is ensured.

[0049] The ornamental layer is not limited to any specific one, but mayinclude various ornamental layers comprising metal films, and ispreferably a hologram layer, that is, a metal film with a relief patternprinted thereupon.

[0050] The acrylic adhesive agent is not limited in its properties, andmay include those with various properties, for example, acrylic adhesiveagents capable of solidifying when exposed to UV rays or to heat.

[0051] The thickness of the coating layer, and the requirements withregard to the water-soluble acrylic resin, polyalkylenimine,polyolefin-based substrate sheet, and ornamental layer are the same withthose given above with respect to the polyolefin-based sheet.

[0052] The polyolefin-based substrate sheet preferably includespolypropylene-based sheets.

[0053] If the sheet is made from polypropylene, the ornamental sheetapplied thereto will entirely have an enhanced strength. If the sheet isenhanced in its transparency, the transparency of the entire ornamentalsheet will be also enhanced.

[0054] Specifically, most preferred are the sheets whose total haze is10% or less when measured by a method based on JIS K7105 as describedabove.

[0055] The coating material for the polyolefin-based resin (PO resin)according to this invention includes an water-soluble acrylic resincontaining a polymer comprising an unsaturated carboxylic acid, andpolyalkylenimine.

[0056] The method by which to process an unsaturated carboxylic acid,polyalkylenimine and a polyolefin-based resin into a sheet is the samewith that given above with respect to the polyolefin-based sheet.

[0057] According to the present invention, because the coating materialcomprises a water-soluble acrylic resin prepared from a polymer of anunsaturated carboxylic acid, and polyalkylenimine, the resulting sheetwill be improved in its printability and protected against thedegradation of its bonding activity which would otherwise result.

[0058] Namely, because the sheet is improved in its printability onaccount of its containing polyalkylenimine, it is amenable to printingbased on common ink.

[0059] If the coating material comprised only polyalkylenimine, theresulting fluid would be so viscous that it would not spread uniformlyover the sheet, which would cause blocking. When a water-soluble acrylicresin is added to the coating material, polyalkylenimine iscross-bridged via ionic bond with the carboxyl group of the acrylicresin, and thus a strong coating film is formed. Moreover, if thecoating material comprises polyalkylenimine and a water-soluble acrylicresin, it is possible to control the content of polyalkylenimine in acoating layer by adjusting the coating amount as appropriate, so thatthe impaired adhesiveness of a cyanoacrylate adhesive agent, which wouldotherwise result due to coexistent polyalkylenimine, can be effectivelyavoided.

[0060] Besides, if another sheet is laid over the coating layer of apolyolefin-based sheet, the resulting laminated structure will beimproved in its mechanical strength.

[0061] The coating material preferably contains volatile amine as anagent for neutralizing the carboxylic group of the acrylic resin.

[0062] The usable volatile amine may include amines having a relativelysmall molecular weight such as ethanolamine (aminoethanol), ammonia,methylamine, ethylamine, etc.

[0063] According to the present invention, because the coating materialcontains volatile amine as a neutralizing agent, an excess amount of thevolatile neutralizer will not remain in the coating layer. Accordingly,it is possible to prevent the degradation of the coating layer, whichwould result if the neutralizer remained in the coating layer.

[0064] Polyalkylenimine preferably has a molecular weight of 200 to20000.

[0065] If polyalkylenimine had a molecular weight more than 20000, itsmiscibility to the water-soluble acrylic resin would be impaired, andthe coating material would have its storage life (pot life) shortened.Moreover, the coating material might develop white precipitate, therebyimpairing the transparency of the sheet assembly. The coating materialwill be free from the above problems, as long as polyalkylenimine has amolecular weight smaller than the above limit. Namely, as long aspolyalkylenimine has a molecular weight smaller than the above limit,the coating material will not pose any problem during processing.However, polyalkylenimine preferably has a molecular weight of 200 orhigher, when its availability is taken into account. More preferably,polyalkylenimine has a molecular weight of 500 to 5000.

[0066] The blending ratio of the water-soluble acrylic resin andpolyethylenimine is preferably 5:1 to 1:4.

[0067] If the blending ratio of polyalkylenimine against the watersoluble alkyl resin were less than 5:1, the resulting coat would nothave sufficient adhesion to the PO sheet. On the other hand, if theblending ratio in question were more than 1:4, the sheets having acoating layer prepared from the material would easily develop blockingwhen overlaid to each other.

[0068] The coating material described above preferably contains anantistatic agent, a natural organic material fine powder, and a UVabsorbing agent as appropriate. The specific examples of those additivesand their addition amounts are as described above with respect to thepolyolefin-based sheet.

BRIEF DESCRIPTION OF DRAWINGS

[0069]FIG. 1 is a sectional view of a part of a polyolefin-based sheetrepresenting a first embodiment of this invention.

[0070]FIG. 2 is a sectional view of a part of an ornamental sheetrepresenting a second embodiment of this invention.

[0071]FIG. 3 is a schematic diagram for illustrating the constitution ofa first system for producing the ornamental sheet of the embodimentshown in FIG. 2.

[0072]FIG. 4 is a schematic diagram for illustrating the constitution ofa second system for producing the ornamental sheet of the embodimentshown in FIG. 2.

BEST MODE FOR CARRYING OUT THE INVENTION

[0073] The preferred embodiments will be described below with referenceto the attached drawings.

[0074] [First Embodiment]

[0075]FIG. 1 shows a polyolefin-based sheet 1 (PO sheet hereinafter)representing a first embodiment of this invention.

[0076] The PO sheet 1 comprises a substrate sheet 10 made of atransparent polypropylene sheet with a coating layer 11 composed of acoating material comprising a water-soluble acrylic resin andpolyalkylenimine formed on a surface upon which an ornamental layer willbe formed.

[0077] The PO sheet constructed as above is prepared as follows.

[0078] A substrate sheet 10 previously processed into a sheet via T-dieextrusion has both its surfaces subjected to corona treatment, that is,oxidization treatment.

[0079] Then, a coating material which has been obtained by blending awater-soluble acrylic resin mainly composed of a copolymer of acrylicacid and methacrylic acid esters, polyethylenimine having a molecularweight of 1200 and an antistatic agent based on sodium sulfonate at aratio of 0.125%:0.025%:0.02% (in terms of the respective weights ofthose solid components with respect to the total weight of the solutionor of the coating material) is applied with a gravure coater onto onesurface of the substrate sheet 10 at a density of 0.0075 g/m² in termsof dry base (or 5 g/m² in terms of wet base). Later, the yield is keptat 80° C. for 30 seconds to be dried, and a PO sheet 1 having a coatinglayer 11 formed thereupon is obtained. The coating process may occurin-line or off-line.

[0080] In this particular embodiment, the blending ratio of thewater-soluble acrylic resin and polyethylenimine is 5:1, and theaddition amount of the antistatic agent is 11.7 wt % with respect to theoverall weight of solid components of the coating material. The coatingdensity of polyethylenimine (in terms of its solid weight) is 0.0012g/m². In addition, the coating layer 11 is allowed to have a thicknessof 0.0075 μm.

[0081] The coating material further contains a specified amount of2-aminoethanol as a volatile neutralizing agent.

[0082] In this process, the coating layer immediately after itsformation has a sufficiently high affinity towards an acrylic adhesiveagent to achieve firm adhesion. However, to further enhance adhesion, itis preferred to subject the sheet assembly to maturation.

[0083] The coating material may be further supplemented with a naturalorganic material fine powder and a UV absorbing agent so that it canhave smooth surfaces and absorb UV rays.

[0084] According to the embodiment as described above, the followingadvantages will be ensured.

[0085] (1) A coating layer 11 composed of a coating material comprisinga water-soluble acrylic resin prepared from a polymer of an unsaturatedcarboxylic acid, and polyalkylenimine covers a surface of a PO substratesheet 10 upon which an ornamental layer will be formed. Accordingly,even when the ornamental layer must be formed via an acrylic adhesiveagent, adhesion of the ornamental layer to the PO sheet 1 will beenhanced. Through this arrangement, it is possible to ensure firmadhesion of the ornamental layer to the PO sheet 1 even when an acrylicadhesive agent is used for adhesion, which would otherwise show a lowaffinity towards the PO sheet.

[0086] (2) Because an acrylic adhesive agent can be used for adhesion,the high transparency of the sheet assembly will be ensured, and thusthe metallic shade of the ornamental layer will serve as an attractivedesign feature when the sheet is used as a package material, that is,the PO sheet 1 will serve as a highly ornamental package material.

[0087] (3) Because the coating layer 11 has a thickness of 0.0075 μm,and the blending ratio of the water-soluble acrylic resin andpolyethylenimine is 5:1 (0.125:0.025), the coating layer 11 is highlyaffinitive to the substrate sheet 10 so that the resulting sheets willrarely develop blocking even when overlaid to each other.

[0088] (4) Because the antistatic agent based on sodium sulfonate isadded at a concentration of 11.7 wt %, the sheet will be protectedagainst the accumulation of static electricity, and blocking of theresulting sheets due to the development of static electricity whichmight otherwise result will be safely avoided. Moreover, addition of anantistatic agent to the coating material will effectively lessen theamount of an antistatic agent to be added to the PO sheet material 10which would be otherwise required, thereby preventing the bleed-out ofan excess amount of that agent which would otherwise result if the sheetcontaining an otherwise required amount of antistatic agent were exposedto high temperatures, that is, the bleed-out which would degrade theappearance of the sheet and its amenability to processing will beeffectively avoided.

[0089] (5) Because polyethylenimine has a molecular weight of 1200, theresulting coat material will have a long pot life, and the coating layer11 therefrom will not form any problem including impaired transparency.

[0090] (6) Because the neutralizing agent is based on volatile2-ethanolamine, an excess amount of volatile neutralizing agent if anywill not remain in the coating layer 11. Accordingly, it is possible toavoid the degradation of the coating layer, which would result if theneutralizer remained in the coating layer 11.

[0091] [Second Embodiment]

[0092] In the following explanation, with regard to the constitutiveelements similar to those of the first embodiment, they will berepresented by the same symbols, and their explanation simplified oromitted.

[0093]FIG. 2 shows an ornamental sheet 2 representing a secondembodiment of this invention.

[0094] The ornamental sheet assembly 2 is obtained by laying a hologramlayer 22 partly made of a metal film via an adhesive layer 21 of anacrylic adhesive agent over a coating layer 11 formed on a PO sheet 1 asdescribed above.

[0095] Turning now to FIG. 3, a first system for producing theornamental sheet assembly 2 and a production method based thereon willbe described.

[0096]FIG. 3 shows the first system 3 for producing an ornamental sheet2 according to the present invention.

[0097] The first production system 3 comprises a feed roll 31 forfeeding a polyester sheet 30; a take-up roll 32 for taking up the sheet30 after the sheet has given out a metal film; a coating roll 33 forcoating an adhesive agent and a metal film; a first pressing roll 34which is placed opposite to the coating roll 33 for pressing the sheet30 towards the coating roll 33; a drying machine 35 for drying theadhesive agent applied to the sheet 30 by the coating roll 33; anembossed copper roll 36 for printing a relief hologram pattern to theadhesive agent; a second pressing roll 37 which is placed opposite tothe printing copper roll 36 for pressing the sheet 30 to the printingcopper roll 36; a pair of transfer rolls 38 for transferring thehologram pattern to a PO sheet 1; and a UV radiating unit 39 forcompletely solidifying the adhesive layer via UV radiation.

[0098] The method for producing an ornamental sheet 2 using the firstproduction system 3 configured as above will be described.

[0099] Firstly, a roll of polyester sheet 30 is set on the feed roll 31.The sheet 30 fed from the feed roll 31 is introduced into a gap betweenthe coating roll 33 and the pressing roll 34 placed opposite to eachother, and here an acrylic adhesive agent capable of solidifying whenexposed to UV rays and supplemented with metal flakes are applied to theentire surface of the sheet 30 while the sheet 30 is pressed by thefirst pressing roll 34 against the coating roll 33.

[0100] Then, the sheet 30 having the adhesive agent coated thereupon iscarried above the drying device 35 and here the adhesive agent is driedso much as to be ready for receiving the printing of a hologram patternthereupon.

[0101] The sheet 30 having the adhesive agent coated thereupon is thenintroduced into a gap between the printing copper roll 36 and the secondpressing roll 37 which are placed opposite to each other, and a patternformed on the printing copper roll 36 is printed onto the adhesivelayer, and thus an adhesive layer having the hologram pattern printedthereupon is formed on the sheet 30.

[0102] In the manner as described above, the sheet 30 carrying theadhesive layer having the hologram pattern printed, and a PO sheet 1prepared as described above with respect to the first embodiment are fedto the pair of transfer rolls 38, 38 such that the sheet 30 issuperimposed over the PO sheet 1, thereby putting the adhesive layer ofthe sheet 30 in contact with the coating layer of the PO sheet 1.Through this process, the adhesive layer with metal flakes having thehologram pattern printed is transferred to the PO sheet 1 to produce asheet assembly having a hologram layer formed thereupon.

[0103] Finally, the ornamental sheet assembly 2 having the hologramlayer formed on the top of it is fed to the UV ray radiating unit 39, sothat the acrylic adhesive agent can be completely solidified.

[0104] The ornamental sheet assembly 2 thus obtained can be used as apackage material for widely varied applications.

[0105] Next, a second system for producing an ornamental sheet assembly2 according to this invention and a production method based thereon willbe described with reference to FIG. 4.

[0106] In the following description, the same constitutive elements withthose of the first production system 3 will be represented by the samesymbols, and their explanation omitted or simplified.

[0107]FIG. 4 shows the second system 4 for producing an ornamental sheetassembly 2 according to this invention.

[0108] The second production system 4 is different from the first one inthe following points.

[0109] With the first production system, the copper printing roll andthe transfer rolls are responsible for the formation of the hologramlayer. However, the second production system 4 includes, instead of thecopper printing roll, second pressing roll and transfer rolls, aprinting surface 42 carrying a hologram pattern and a heating plate 41which moves up and down, at its terminal end.

[0110] The second production system 4 is adapted for transferring ahologram layer using the heating plate 41, and for employing athermosetting acrylic adhesive agent, and thus can dispense with the useof a UV ray radiating unit.

[0111] A sheet assembly 40 is obtained by forming an easily separablelayer such as a silicon coat on a polyester substrate sheet, and then bylaying a metal film over the sheet via vapor deposition.

[0112] The method how to produce an ornamental sheet 2 using the secondproduction system 4 configured as above will be described.

[0113] Firstly, an easily separable layer such as a silicon coat isformed in advance on a polyester substrate sheet, and a metal film isformed via vapor deposition on the sheet. A roll of such a sheetassembly 40 is set on a feed roll 31.

[0114] The sheet assembly 40 fed from the feed roll 31 is introducedinto a gap between a coating roll 33 and a pressing roll 34 which areplaced opposite to each other, and here a thermosetting acrylic adhesiveagent is coated onto the entire surface of the metal film while thesheet assembly 40 is pressed by the pressing roll 34 against the coatingroll 33. The sheet assembly 40 having thus the adhesive agent coatedthereupon is carried above a PO sheet 1 placed in advance beneath theheating plate 41. Then, the heating plate 41 lowers and the sheetassembly 40 also descends being forced down by a printing surface 42, sothat the sheet assembly 40 is put into contact with the PO sheet 1. Theadhesive agent, which has a hologram pattern printed being pressed bythe printing surface 42 and hardens in the presence of heat istransferred to the PO sheet 1, to produce an ornamental sheet 2.

[0115] According to the second embodiment as described above, inaddition to the aforementioned advantages obtained from the firstembodiment, the following advantages will be further ensured.

[0116] (7) Because the sheet assembly comprises the coating layer 11containing polyethylenimine on the surface of the PO substrate sheet 10,adhesion of the PO sheet 1 to the adhesive layer 21 comprising anacrylic adhesive agent will be enhanced, and as a result adhesion of thePO sheet 1 to the ornamental layer 22 will be also enhanced. Moreover,because the acrylic adhesive agent is used, the resulting ornamentalsheet 2 will be able to maintain its transparency.

[0117] It should be noted that the present invention is not limited toany one of the above embodiments, but include any variants andmodifications of them, as long as those variants and modifications cansatisfy the objects of this invention.

[0118] For example, according to the above embodiments, the PO substratesheet incorporates a polypropylene-based (PP) sheet. However, thesubstrate sheet is not limited to this one, but may include PO substratesheets composed of various other polyolefins. The above embodimentsdepend on T-die extrusion for molding the substrate sheet 10, but themolding method is not limited to this one. The sheet molding can occurby any known method such as calendaring, casting or the like.

[0119] The above embodiments employ a water-soluble acrylic resin mainlycomprising a copolymer of acrylic acid and methacrylic acid esters.However, the usable water-soluble acrylic resin is not limited to thisone, but may include any water-soluble resins comprising polymers ofvarious unsaturated carboxylic acids. The other component of the coatingmaterial is not limited to polyethylenimine, but may includepolypropylenimine and the like. The blending ratio of the water-solubleacrylic resin and polyethylenimine in the formation of the coatingmaterial is not limited to those cited with respect to the aboveembodiments, but may take any value between 5:1 and 1:4.

[0120] According to the above embodiments, the coating density is set at0.0075 g/m² in terms of dry base. However, the coating density is notlimited to this level, but may take any appropriate value depending ongiven situations. For example, the coating may occur at 0.01 or 0.005g/m² in terms of dry base.

[0121] The method and mode of oxidization treatment applied to thesubstrate sheet 10 are not limited to those employed in the aboveembodiments: the treatment may be applied to both surfaces of asubstrate sheet, or to either of them depending on given situations, ormay occur by any other oxidization method than corona discharge, forexample, by frame treatment. The usable coater is not limited to agravure coater, but may include any coaters such as an offset coater.The drying temperature and the drying time can be also set at anydesired values, depending on the property of the coating material andthe thickness of the coating layer.

[0122] The antistatic agent is not limited to one based on sodiumsulfonate, but may include any appropriate antistatic agents dependingon given situations. The addition amount of the antistatic agent can beset at any desired level between 0.5 and 30 wt %, preferably between 2and 15 wt %.

[0123] In the second embodiment, vapor deposition is employed fordepositing a metal film on a polyester-based sheet to produce thereby asheet assembly 40. However, the method for forming a metal film on apolyester-based sheet is not limited to above, but may includesputtering, ion-plating, etc.

[0124] The specific structures and shapes of the instruments andelements required for achieving the above embodiments can be modifiedand altered in any desired manner as long as the modifications andalterations are in compliance with the achievement of the object of thepresent invention.

[0125] [Third Embodiments]

[0126] This embodiment relates to the production of a package materialby employing a polyolefin-based sheet like the substrate sheet of thefirst embodiment, and by subjecting the sheet to secondary processingsuch as printing or bonding on one of its surfaces without, in contrastwith the first embodiment, forming an ornamental layer on that processedsurface. Because the basic composition of the polyolefin-based sheet andthe formation of a coating layer prepared from a coating material arethe same with those of the first embodiment, and thus their explanationwill be omitted.

[0127] In this embodiment, the coating layer formed on the surface ofthe PO sheet presents with improved printability immediately after itsformation. However, to enhance the mechanical strength of the coatinglayer, it is preferred to subject the sheet to maturation.

[0128] The PP sheet assembly prepared as above is suitably used forvarious applications as indicated in the following because of the easewith which the assembly is amenable to printing and bonding.

[0129] (1) Display Sheet

[0130] “Display sheet” used herein refers to a protective sheet to serveas a printing base of a signboard.

[0131] The PP sheet is highly useful when it is employed in displayapplications: the PP sheet has an improved printability andadhesiveness; the PP sheet is easily provided with antistatic activity;and it is highly strong and transparent.

[0132] (2) Package Sheet

[0133] The PP sheet is highly useful when it is employed in packagingapplications: the PP sheet is excellent in transparency andprintability; and it is so affinitive to cyanoacrylate adhesives that itis also amenable to secondary processing.

[0134] (3) Transparent Recording Sheet (Film)

[0135] “Transparent recording sheet” used herein refers to a sheet usedfor a signboard to be placed in a railway station or other facilitieswhich is illumined from rear with a light source such as a fluorescentlight (back-light).

[0136] The PP sheet is highly useful when it is employed as atransparent recording sheet: it will easily receive a printable coatinglayer on its surface because it is easily amenable to printing andbonding, and thus printing based on an ink jet printer can be easilyapplied thereto; it is so transparent that it does not interfere withthe illuminating effect of the back-light; it is so affinitive to theoverlying printing coat and so transparent that contrast of printedimages with the background is emphasized; and it readily amenable todirect printing such as offset printing, gravure printing, etc.

[0137] (4) Cosmetic Sheet (Film)

[0138] The PP sheet is highly useful when it is employed as a cosmeticsheet (film): it is so amenable to printing that it allows printing withcommon ink; it allows the coating layer to have antistatic activity soeasily that sheet feed is improved and thus printing speed elevated;introduction of the coating layer having antistatic activity willdispense with the use of an antistatic agent for the substrate sheetwhich will lower the failure resulting from after-treatments (printing,bonding, etc.) which would be otherwise required to cope with adverseeffects emerging according to the progression of seasons; and it isreadily amenable to bonding based on an cyanoacrylate-based adhesivelike ordinary resin sheets, that is, it readily receive the bonding of apiece of paper, wood or metal via a common adhesive agent.

[0139] (5) Emblem Sheet

[0140] “Emblem sheet” used herein refers to a sheet used for seal,label, sticker, etc.

[0141] The PP sheet is highly useful when it is employed as an emblemsheet: it is so amenable to printing that printing using an inexpensivecommon ink is possible; it is so amenable to bonding that it easilyreceives an adhesive layer; and it is so affinitive to the adhesivelayer that it serves itself for various bonding applications.

[0142] The present embodiment having the features as described abovewill ensure following advantages.

[0143] (1) Because the sheet assembly is highly amenable to printingbecause of its incorporating polyalkylenimine, it allows printing basedon common ink.

[0144] (2) Because the sheet assembly incorporates the coating material,which comprises polyethylenimine and a water-soluble acrylic resinblended at an appropriate ratio, it is protected against loweredadhesiveness, which would result if it incorporated onlypolyethylenimine.

[0145] (3) Because the coating layer has a thickness of 0.0075 μm, andthe blending ratio of the water-soluble acrylic resin andpolyethylenimine is 5:1 (0.125:0.025), the coating layer is highlyaffinitive to the substrate sheet so that the resulting sheets willhardly develop blocking even when overlaid to each other.

[0146] (4) Because the coating density of polyethylenimine is set at0.0012 g/m², it is possible to maintain the improved printability of thePP sheet, and not to interfere with the adhesiveness of an cyanoacrylateadhesive agent even when it is put into contact with the adhesive agent.

[0147] (5) Because the PP sheet is supplemented with an antistatic agentbased on sodium sulfonate at a concentration of 11.7 wt %, it isprovided with antistatic activity, and thus it is protected againstblocking which would occur if PP sheets with excess static electricityare overlaid to each other, and thus against impaired sheet feed whichwould be encountered with such sheets with excess statistic electricity.Moreover, addition of an antistatic agent to a coating material willeffectively lessen the amount of an antistatic agent to be added to a PPsheet material which would be otherwise required, thereby preventing thebleed-out from the sheet of the agent which would result if the sheetcontaining an otherwise required amount of antistatic agent were exposedto high temperatures, that is, the bleed-out which would degrade theappearance of the sheet and its amenability to processing will beeffectively avoided.

[0148] (6) Because polyethylenimine has a molecular weight of 1200, theresulting coat material will have a long pot life, and the coattherefrom will not form any problem including the one with regard to itstransparency.

[0149] (7) Because the neutralizing agent is based on volatile2-ethanolamine, the volatile neutralizing agent will not remain in thecoating layer. Accordingly, it is possible to avoid the degradation ofthe coating layer, which would result if the neutralizer remained in thecoating layer.

[0150] The various variants cited with respect to the first embodimentwill be also deducible from the present embodiments.

EXAMPLES

[0151] Examples and comparative examples will be described below forfurther illustrating the present invention.

[0152] Examples 1 to 5 are based on the first and second embodimentswhile Comparative Examples 1 and 2 are given for comparison.

[0153] Example 6 is based on the third embodiment described above, andComparative Example 3 is introduced so that the pot life is comparedbetween the two.

[0154] Examples 7 to 9 are based on the third embodiment, whileComparative Examples 4 to 7 are given for comparison.

Example 1

[0155] A coating material was prepared by using following materials, anda PO sheet assembly having a coating layer was prepared by the methoddescribed with respect to the first embodiment. Then, the sheet assemblywas applied to the first production system described with respect to thesecond embodiment with aluminum used as a non-iron metal for the metalfilm, to produce an ornamental sheet assembly.

[0156] The coating layer had a thickness of 0.0075 μm.

[0157] (1) Water-soluble acrylic resin: copolymer of acrylic acid andmethacrylic acid esters.

[0158] (2) Polyalkylenimine: polyalkylenimine having a molecular weightof 1200.

[0159] (3) Antistatic agent: sodium sulfonate-based surfactant.

[0160] (4) Blending ratio of water-soluble acrylic resin topolyethylenimine: 0.125 (g/m²)/0.025 (g/m²)=5/1.

[0161] (5) Addition amount of antistatic agent: 11.7 wt %.

Example 2

[0162] Another ornamental sheet assembly was obtained by the same methodas in Example 1 except that the coating density of polyethylenimine isset at 0.025 (g/m²), and that the coating layer had a thickness of 0.03μm.

Example 3

[0163] A still further ornamental sheet assembly was obtained by thesame method as in Example 1 except that the coating density ofpolyethylenimine is set at 0.0625 (g/m²), and that the coating layer hada thickness of 0.09 μm.

Example 4

[0164] A still further ornamental sheet assembly was obtained by thesame method as in Example 1 except that the coating density ofpolyethylenimine is set at 0.0005 (g/m²), and that the coating layer hada thickness of 0.007 μm.

Example 5

[0165] A still further ornamental sheet assembly was obtained by thesame method as in Example 1 except that the coating density ofpolyethylenimine is set at 0.0125 (g/m²), and that the coating layer hada thickness of 0.04 μm.

Comparative Example 1

[0166] An ornamental sheet assembly was obtained by the same method asin Example 1 except that no coating layer was formed on the substratesheet.

Comparative Example 2

[0167] Another ornamental sheet assembly was obtained by the same methodas in Example 1 except that no coating layer was formed on the substratesheet, and that the adhesive agent is a urethane-based adhesive agent.

[0168] The ornamental sheet assemblies obtained in the above Examplesand Comparative Examples were evaluated in terms of their transparencyand affinity to the metal film (ornamental layer), and the results arelisted in Table 1.

[0169] If a given test sheet assembly is found to be equal intransparency to the substrate sheet or the PO sheet, it is marked by“A”. If the test sheet assembly is found to be inferior in transparencyto the substrate or the PO sheet, it is marked by “C”.

[0170] Adhesion of the ornamental layer to the substrate sheet wastested and evaluated as follows: a piece of cellophane tape was appliedonto the surface of the ornamental layer; the tape was vigorously pulledapart from the surface in a direction orthogonal to the surface; andadhesion of the ornamental layer was evaluated. The evaluation resultwas marked as follows: “A” for a case where no ornamental layer is tornoff; “B” for a case where a part of the ornamental layer is torn off;and “C” for a case where a large part of the ornamental layer is tornoff.

[0171] It is seen from Table 1 that the ornamental sheet assembliesobtained in Examples 1 to 3 are excellent in transparency andadhesiveness because they comprise a coating layer on a substrate sheet,and include a hologram layer and the PO sheet bonded together with anacrylic adhesive agent.

[0172] In contrast, it is seen from the table that the ornamental sheetassembly obtained in Comparative Example 1 is impaired in itsadhesiveness because it does not have sufficient adhesion to theadhesive layer of an acrylic resin adhesive agent which is accounted forby the lack of the coating layer.

[0173] It is also seen from the table that the ornamental sheet assemblyobtained in Comparative Example 2 is impaired in transparency, thoughmaintaining sufficient adhesiveness in spite of its lacking the coatinglayer, because it incorporates a urethane-based adhesive agent. TABLE 1Coating layer Transparency Adhesiveness Example 1 Acrylic A A Example 2Acrylic A A Example 3 Acrylic A A Example 4 Acrylic A B Example 5Acrylic A B Comparative Acrylic A C Example 1 Comparative Acrylic C BExample 2

Example 6

[0174] A coating material was prepared from the following constituents,and its pot life was determined.

[0175] (1) Water-soluble acrylic resin: copolymer of acrylic acid andmethacrylic acid esters.

[0176] (2) Polyalkylenimine: polyalkylenimine having a molecular weightof 600.

[0177] (3) Antistatic agent: sodium sulfonate-based surfactant.

[0178] (4) Blending ratio of water-soluble acrylic resin topolyethylenimine: 0.0125 (g/m²)/0.25 (g/m²)=5/1.

[0179] (5) Addition amount of antistatic agent: 11.7 wt %.

Comparative Example 5

[0180] A coating material was prepared from the same constituentsblended at the same ratio as in Example 6 except that polyethyleniminehas a molecular weight of 70,000.

[0181] The coating materials obtained in Example 6 and ComparativeExample 3 were determined of their pot life, and the results are shownin Table 2.

[0182] It is seen from the table that the coating material of Example 6which incorporates polyethylenimine having a molecular weight of 600 hasa pot life over 8 hours, that is, the life is markedly prolonged ascompared with the coating material of Comparative Example 3 whichincorporates polyalkylenimine having a molecular weight of 70,000 andwhich has a pot life less than 2 hours. TABLE 2 Pot life Example 6 >8Comparative Example 3 <2

[0183] Next, various coating materials were prepared with the blendingratio of the water-soluble acrylic resin and polyethylenimine varied,and what influence the coats prepared from those coating materials haveon the PO sheet assembly was studied.

Example 7

[0184] A test coating material was applied on both surfaces of a PPsheet by the method described above with respect to the embodiments, toproduce a PP sheet assembly with coating layers on both surfaces.

[0185] The coating material was prepared from the same constituentsblended at the same ratio as in Example 6 except that polyethyleniminehas a molecular weight of 1,200.

Example 8

[0186] A PP sheet assembly with coating layers on both surfaces wasobtained as in Example 7 except that the blending ratio of thewater-soluble acrylic resin and polyethylenimine was made 1:4(0.125:0.5).

Example 9

[0187] A PP sheet assembly with coating layers on both surfaces wasobtained as in Example 7 except that the blending ratio of thewater-soluble acrylic resin and polyethylenimine was made 1:2(0.625:1.25).

Comparative Example 4

[0188] A PP sheet (having received corona treatment) with no coatingmaterial coated thereupon was served for test.

Comparative Example 5

[0189] A PP sheet assembly with coating layers on both surfaces wasobtained as in Example 7 except that the blending ratio of thewater-soluble acrylic resin and polyethylenimine was made 12.5:1(0.125:0.01).

Comparative Example 6

[0190] A PP sheet assembly with coating layers on both surfaces wasobtained as in Example 7 except that the blending ratio of thewater-soluble acrylic resin and polyethylenimine was made 25:1(0.625:0.025).

Comparative Example 7

[0191] A PP sheet assembly with coating layers on both surfaces wasobtained as in Example 7 except that the blending ratio of thewater-soluble acrylic resin and polyethylenimine was made 1:10(0.125:1.25).

[0192] The PP sheet assemblies obtained in Examples 7 to 9 and inComparative Examples 4 and 5 were tested and evaluated for theirtransparency, resistance to blocking, easiness for cutting, printability(easiness for sheet feed, and affinity to ink), and adhesiveness (tocyanoacrylic adhesive agents and to wood), and the evaluation resultsare shown in Table 3. The table also lists the data regarding thethickness of the test sheet assemblies, and the coating density ofpolyethylenimine. TABLE 3 Thickness Coating density of coating ofpolyethyl- Trans- Resistance Easiness Affinity to ink Affinity to inkAdhesiveness to Adhesiveness layer (μm) enimine (g/m²) parency toblocking for cutting (UV offset) (general UV ink) cyanoacrylate to woodExample 7 0.0075 0.0012 A A A A A A A Example 8 0.03 0.025 A A A A A A AExample 9 0.09 0.0625 A A A A A A A Comparative — — A A A C C A CExample 4 Comparative 0.007 0.0005 A A A C C C C Example 5 Comparative0.04 0.0125 A A A C C C C Example 6 Comparative 0.007 0.0625 A C C A A CA Example 7

[0193] The various properties cited in Table 3 of the test sheetassembly were determined and evaluated as follows.

[0194] (1) Transparency

[0195] The test sheet assembly was determined of its haze by a methodbased on JIS K-7105. If a test sheet assembly gave haze of 3.0% or less,it was judged satisfactory (“A”).

[0196] (2) Resistance to Blocking (Anti-blocking Property)

[0197] PP sheet assemblies (0.3 t) were laid one over another until theheap reached a height of 1.5 m, and the heap was left for 24 hours, andevaluated as follows according to the presence of blocking.

[0198] If all sheet assemblies did not change in appearance, and theywere easily separated from each other, the sheet assembly was judgedsatisfactory (“A”).

[0199] If all sheet assemblies did not change in appearance, and theywere separated from each other without forming any practical problem,although slight blocking was observed, the sheet assembly was judgedfair (“B”).

[0200] If some sheet assemblies changed in appearance, and could not beseparated from each other as a result of blocking, the sheet assemblywas judged inadequate (“C”).

[0201] (3) Easiness for Cutting

[0202] Sheet assemblies were cut into pieces with a cutter, and piecesfrom different sheet assemblies were laid one over another, and the heapwas checked for the presence of blocking. The evaluation standard wasthe same as in the section (2).

[0203] (4) Printability

[0204] (4-1) Easiness for Sheet Feed

[0205] A heap of sheet assemblies were prepared, and they were checkedwhether they could be smoothly fed to a UV offset printing machine at arate of 8000 sheets/hour. If they were found to be smoothly fed, theireasiness for sheet feed was judged satisfactory (“A”). If they could notbe smoothly fed, their easiness for sheet feed was judged inadequate(“C”).

[0206] (4-2) Affinity to Ink

[0207] A piece of cellophane tape was applied to a printed surface of asheet assembly, and the tape was vigorously pulled apart from thesurface in a direction orthogonal to the surface, and the affinity ofthe sheet assembly to ink was evaluated as follows.

[0208] If the printed ink did not separate, the affinity of the sheetassembly to ink was judged satisfactory (“A”).

[0209] If a part of the printed ink separated, the affinity of the sheetassembly to ink was judged fair (“B”).

[0210] If a large part of the printed ink separated, the affinity of thesheet assembly to ink was judged inadequate (“C”).

[0211] (5) Adhesiveness

[0212] (5-1) Adhesiveness to Cyanoacrylate

[0213] Two PP sheet assemblies were prepared; one had a cyanoacrylateadhesive agent applied on one surface after the application of a primer;and the other was applied to the coated surface of the former foradhesion. The two bonded sheet assemblies were mechanically separated,and the adhesiveness of the sheet assembly to cyanoacrylate wasevaluated according to the exertion required for the separation.

[0214] If the force required for separation is sufficient for breakingthe sheet assembly itself, the adhesiveness of the sheet assembly tocyanoacrylate was judged satisfactory (“A”).

[0215] If the force required for separation is below the level at whichthe sheet assembly itself would break, the adhesiveness of the sheetassembly to cyanoacrylate was judged inadequate (“C”).

[0216] (5-2) Adhesiveness to Wood

[0217] A wood slab is bonded via a wood adhesive agent in the form of aresin emulsion to a sheet assembly, and the adhesiveness of the sheetassembly to wood was evaluated according to the following standard.

[0218] If a force of 9.8 N/1.5 cm or higher is required for separatingthe wood from the sheet assembly, the adhesiveness of the sheet assemblyto wood was judged satisfactory (“A”).

[0219] If a force less than 9.8 N/1.5 cm is required for separating thewood from the sheet assembly, the adhesiveness of the sheet assembly towood was judged inadequate (“C”).

[0220] It is seen from Table 3 that the sheet assemblies of Examples 7to 9 are far more excellent in the affinity to ink and adhesiveness tocyanoacrylate and to wood than corresponding Comparative Examples,because the former includes the water-soluble acryl resin andpolyethylenimine at a ratio in the range of 5:1 to 1:4. It is also seenfrom the table that the sheet assemblies of the Examples are moreexcellent in transparency, resistance to blocking and easiness forcutting than the corresponding Comparative Examples, and that the formeris more excellent in easiness for sheet feed than the latter because theformer receives the addition of a specific amount of an antistaticagent.

[0221] On the other hand, because Comparative Example 4 is a neat PPsheet with no coating layer applied, it incorporates nopolyethylenimine, and thus its adhesiveness to cyanoacrylate isexcellent. However, its adhesiveness to wood is low and its affinity toink is also low.

[0222] The sheet assemblies of Comparative Examples 5 and 6 incorporatethe water-soluble acrylic resin and polyethylenimine at ratios of 12.5:1and 25:1, respectively. The fraction of polyethylenimine is considerablylow when compared with the value of corresponding Examples, which mayaccount for the low affinity to ink of the sheet assemblies of theComparative Examples here concerned.

[0223] The sheet assembly of Comparative Example 7 incorporates thewater-soluble acrylic resin and polyethylenimine at a ratio of 1:10which indicates the fraction of polyethylenimine is considerably higherthan in the corresponding Examples. This may account for the fact thatthe sheet assembly in question is low in adhesiveness and tends todevelop blocking although its affinity to ink is improved.

[0224] Industrial Availability

[0225] The sheet assembly of the present invention is applicable as apolyolefin-based sheet for packing, or more specifically is utilizableas a display sheet, package sheet, transparent recording sheet, cosmeticsheet, and emblem sheet, and a coating material to be used for theformation of a coating layer on the above sheet.

1. A polyolefin-based sheet comprising a coating layer composed of acoating material comprising a water-soluble acrylic resin andpolyalkylenimine.
 2. A polyolefin-based sheet as described in claim 1wherein the coating layer has a thickness of 0.003 to 0.1 μm, and theblending ratio of the water-soluble alkyl resin and polyalkylenimine isin the range of 5:1 to 1:4.
 3. A polyolefin-based sheet as described inclaim 2 wherein the coating amount of polyalkylenimine is in the rangeof 0.0005 to 0.1 g/m².
 4. A polyolefin-based sheet as described in anyone of claims 1 to 3 wherein the coating layer contains 0.5 to 30 wt %antistatic agent with respect to the overall weight of solid componentsof the coating material.
 5. A polyolefin-based sheet as described in anyone of claims 1 to 4 wherein the coating layer contains a naturalorganic material fine powder and/or a ultra-violet ray absorbing agent.6. A polyolefin-based sheet as described in any one of claims 1 to 5wherein the polyolefin-based sheet is a polypropylene-based sheet.
 7. Adisplay sheet incorporating a polyolefin-based sheet as described in anyone of claims 1 to
 6. 8. A package sheet incorporating apolyolefin-based sheet as described in any one of claims 1 to
 6. 9. Atransparent recording sheet incorporating a polyolefin-based sheet asdescribed in any one of claims 1 to
 6. 10. A cosmetic sheetincorporating a polyolefin-based sheet as described in any one of claims1 to
 6. 11. An emblem sheet incorporating a polyolefin-based sheet asdescribed in any one of claims 1 to
 6. 12. A polyolefin-based sheet asdescribed in any one of claims 1 to 6 comprising a polyolefin-basedsubstrate sheet which will have a metal-containing ornamental layerformed at least on one of its surfaces, and a coating layer on thesurface upon which the ornamental layer will be formed, wherein thecoating layer is composed of a coating material comprising awater-soluble acrylic resin prepared from a polymer of an unsaturatedcarboxylic acid, and polyalkylenimine.
 13. A polyolefin-based sheet asdescribed in claim 12 wherein the unsaturated carboxylic acid is acrylicacid and/or methacrylic acid.
 14. A polyolefin-based sheet as describedin claim 12 or 13 wherein the ornamental layer is a hologram layer. 15.An ornamental sheet comprising: a polyolefin-based substrate sheethaving a coating layer composed of a coating material comprising awater-soluble acrylic resin and polyalkylenimine; an acrylic adhesivelayer formed on the coating layer; and an ornamental layer formed on theacrylic adhesive layer.
 16. An ornamental sheet as described in claim 15wherein the ornamental sheet contains a metal.
 17. An ornamental sheetas described in claim 15 or 16 wherein the ornamental layer is ahologram layer.
 18. An ornamental sheet as described in any one ofclaims 15 to 17 wherein the thickness of the coating layer is 0.003 to0.1 μm, and the blending ratio of the water-soluble acrylic resin andpolyalkylenimine is 5:1 to 1:4.
 19. An ornamental sheet as described inany one of claims 15 to 18 wherein the coating amount ofpolyalkylenimine is 0.0005 to 0.1 g/m².
 20. An ornamental sheet asdescribed in any one of claims 15 to 19 wherein the coating layercontains an antistatic agent at 0.5 to 30 wt % in terms of its weightagainst the overall weight of solid components of the coating material.21. An ornamental sheet as described in any one of claims 15 to 20wherein the coating layer contains a natural organic material finepowder and/or a ultra-violet ray absorbing agent.
 22. An ornamentalsheet as described in any one of claims 15 to 21 wherein thepolyolefin-based substrate sheet is a polypropylene-based sheet.
 23. Anornamental sheet as described in any one of claims 15 to 22 wherein thetotal haze of the polyolefin-based substrate sheet is 10% or less.
 24. Acoating material for polyolefin-based resins comprising a water-solubleacrylic resin containing a polymer of an unsaturated carboxylic acid,and polyalkylenimine.
 25. A coating material for polyolefin-based resinsas described in claim 24 wherein the unsaturated carboxylic acid isacrylic acid and/or methacrylic acid.
 26. A coating material forpolyolefin-based resins as described in claim 24 or 25 furthercomprising volatile amine as an agent for neutralizing the carboxylicgroup of the water-soluble acrylic acid.
 27. A coating material forpolyolefin-based resins as described in any one of claims 24 to 26wherein the molecular weight of polyalkylenimine is 200 to
 20000. 28. Acoating material for polyolefin-based resins as described in any one ofclaims 24 to 27 wherein polyalkylenimine is polyethylenimine.
 29. Acoating material for polyolefin-based resins as described in claim 24wherein the blending ratio of the water-soluble acrylic resin andpolyethylenimine is 5:1 to 1:4.
 30. A coating material forpolyolefin-based resins as described in any one of claims 24 to 29further comprising an antistatic agent.
 31. A coating material forpolyolefin-based resins as described in claim 30 wherein the antistaticagent is added at 0.5 to 30 wt % with respect to the overall weight ofsolid components of the coating material.
 32. A coating material forpolyolefin-based resins as described in any one of claims 24 to 31wherein the coating layer contains a natural organic material finepowder, and/or its solubilized substance.
 33. A coating material forpolyolefin-based resins as described in any one of claims 24 to 32further comprising a ultra-violet ray absorbing agent.